Perhaps you should try some spelling variations:
phan duc » pham duc, phan tu, phan dau
sach ky » sach y, sach ty, sach kem
hieu vi » hieu voi, hieu va, hieu ve
vi phan » va phan, vi pham, ve phan
va hanh » van hanh, va thanh, va danh
hanh va » hang va, hanh vi
sac ky » cac ky, sai ky
va cua » va chua, via cua, ca cua
cua su » qua su
x hoi » xa hoi, o hoi, 5 hoi

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: so ((sach ky) OR (sac ky)) nang ((x hoi) or (x ho)). hieu vi phan duc va hanh va cua su~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach ky) OR (sac ky)) nang ((x hoi) OR (x ho)). hieu vi phan duc va hanh va cua su.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach ky) OR (sac ky)) nang ((x hoi) or (x ho)). hieu vi phan duc va hanh va cua su".
• Adding a wildcard symbol may retrieve word variants: so ((sach ky) OR (sac ky)) nang ((x hoi) or (x ho)). hieu vi phan duc va hanh va cua su*.